Piston



Aug. 12, 1930. J DUSEVOIR 1,772,931

PISTON Filed March 20, 1929 2 Sheet'sSheet l I N V EN TOR. QQMWM A TTORNEYb.

Aug. 12, 1930. DUSEVQIR 1,772,931

PISTON Filed March 20, 1929 2 Sheets-Sheet 2 INVEN TOR. @ELAW gz/zm 0? ATTORNEYS.

Patented Aug. 12, 1930 UNITED STATES PATENT OFFICE JULIUS DUSEVOIB, F OAKLAND, CALIFORNIA, ASSIGNOR T0 MOTIVE DEVICES, ENG, OF SAN FRANCISCO, CALIFORNIA, A CORPORATION OF CALIFORNIA PISTON Application filed March 20, 1929. Serial No. 848,592.

This invention relates to pistons, and especially to pistons of the type used in internal combustion engines and the like.

The object of the present invention is to generally improve and simplify the construction and operation of pistons of the character described; to provide a piston which is adapted to be constructed of aluminum or its a1- loys; to provide a piston which is machined or ground to present a major and a minor axisand provided with an internal expansion member engageable with the minor axis so as to cause expansion of said axis and contraction of the major axis as the piston increases in temperature during operation; to provide a piston structure which permits the use of a thin flexible skirt portion, and which is provided with means for supporting and reinforcing the pressure side of the skirt; and further to provlde means on the skirt proper for collecting oil and for directing the oil to the pressure side of the skirt where lubrication is most essential.

The piston is shown by way of illustration in the accompanying drawings, in which:

Fig. 1 shows a side elevation of the piston,

Fig. 2 shows an elevation taken at right angles to Fig. 1, the drawing being partially in section,

Fig. 3 is a cross section taken on line III-III of Fig. 1,

Fig. 4 is an end view of the lowerend of the piston, taken on line IVIV of Fig. 1,

Fig. 5 is a view similar to Fig. 1, with the outer piston skirt entirely removed,

Fig. 6 is a diagrammatic view of a cylinder, a piston, a crank shaft, and a connecting rod.

Referring to the drawings in detail, and particularly to Figs. 1, 2 and 5, A indicates the head of the piston, 2 the ring portion, 3 the inner skirt or. expansion member, 4 a

pair of wrist pin bosses supported thereby,

lower end of the inner skirt up to the wrist pin bosses, as shown in Figs. 1 and 2, while the rib 6 extends from the bottom of the inner skirt substantially up to the ring portion,

being spaced therefrom approximately or so, as is clearly shown in Fig. l. The outer skirt extends a slight distance below the inner skirt and the lugs 6, 7 and 8, and the upper edge of the outer skirt extends to the top of the lug 6, the entire top portion of the skirt being thus separated from the ring portion of the head by an eighth of an inch or so. The outer skirt is'furthermore cut away around the wrist pin bosses, the cut away portion presenting two inclined sides, such as indicated at 9 and 10, and a lower rounded portion 11. This cutting away of the outer skirt relieves the piston of excess metal and weight, and as will hereinafter be described, may just-as well be cut away, as the pressure or contact of this portion of the skirt with relation to the cylinder wall is so small as to be negligible, the main contact between the outer skirt and the cylinder wall being between the surfaces disposed at right angles to the wrist pin bosses, or the surfaces indi cated at 12 and 13. The cut away portions of the skirt give the outer skirt the appearance of two shoes, such as indicated at 12 and 13, which are connected by a lower ring portion, or the portion formed below the rounded cut away portion indicated at 11.

The inner skirt or expansion member 3 is also cut away to reduce the weight of the piston to a minimum,the cut away portion being indicated at 14. The inner skirt thus forms a complete circle on the line IIIIII, see Fig. 3 but the lower end presents a half circle only, see the lower end view of the piston illustrated in Fig. 4.

By referring to Fig. 6 it will be noted that the connecting rod 15 is pivoted directly to the piston by means of a wrist pin 16, and the lateral component of the thrust which rewardly in the direction of arrows e.

sults from the explosion and its reaction upon the connecting rod operates at right angles to the axis of the wrist pin. This forces one side of the piston indicated at 17, a ainst the cylinder wall during the downwar or working stroke. I hence refer to this side of the piston as the pressure side, and the other side of the iston indicated at 18 as the non-pressure si e.

By referring to Figs. 1, 2 and 5 it will be noted that the skirt 5 is supported by the lug 6 and the lugs 7 and 8, while the nonpressure side of the skirt is entirely unsupported except at the points 7 and 8. This is important as it leaves the unsupported side of the skirt in a condition where it may be flexed.

In actual practice, when machining the piston, the sides adjacent the ends of the wrist pin bosses are ground away or relieved a few thousandths of an inch, the ground away portion being indicated by the arrow 0?. The sides parallel to the wrist pin indicated at 13 and 14 are machined and ground to fit the inner contour of the cylinder hence, when the piston is placed in the cylinder close contact is maintained between the surfaces13and14and the cylinder wall, while a few thousands of an inch clearance is maintained at the points indicated by the arrows d. A small clearance is of course allowed between the surfaces 13 and 14, at least suflicient to maintain a proper lubricating oil film.

When the piston is in operation and the head is subjected to the tem erature produced by combustion, heat is con ucted downwardly through the inner skirt and as the major portion of the inner skirt represents an arch member, the free ends thereof indicated at 17 and 18 will have a tendency to expand out- Such outward expansion of the inner skirt or arch member is transmitted through the lugs 7 and 8 to the ground away sides of the outer skirt and these may thus be forced outwardly as they are free to do so. Outward expansion of the relief sides of the skirt will obviously pull in the unsupported side of the skirt indicated at 14, and this will have a tendency to assume the dotted line position indicated at 14*. Hence, if an aluminum or aluminum alloy piston is employed it is possible to fit the shoes as snugly as a cast iron piston, as the expansion caused by the inner arch member will force the relieving sides of the skirt outwardly and will at the same time proportionately pull the unsupported side of the skirt inwardly. The amount of outward and inward expansion that takes place is in proportion to the co-efiicient of expansion of the metal. A snug fit is thus maintained under all conditions whether hot or cold and seizing or binding of the skirt is avoided.

It was previously stated that the outer skirt could be cut away adjacent the wrist pin bosses as indicated at 9, 10 and 11 without materially afi'ecting the bearing surface presented b the skirt. It is believed that this will be 0 early understood at this time as it is more or less obvious that the major stresses and pressures are absorbed by. the skirt portion 13 and also partly by the skirt portion indicated at 14. comparatively few, if any, stresses are exerted on the sides of the skirt adjacent the ends of the wrist pin and it is for this reason that the area there presented may be reduced to a minimum.

By referring to Fig. 1 it will be noted that the top of the skirt portion indicated at 13 is grooved as indicated at 20, and so are the inclined sides of the cut away portion indicated at 9 and 10. The groove 20 connects with the groove 21 formed in the face of the skirt portion indicated at 13, the upper edge portion of the skirt functioning as more or less of a scraper. The oil removed by the scraper action is collected by the groove 20. It drains down the rooved inclined sides 10, and as these are irected into the groove 21 the oil is collected and distributed at a point where it most effectively maintains an oil film between the piston and the cylinder. The groove 21 will at all times remain filled with oil, thus insuring ample lubrication and particularly insuring lubrication at the time of starting, this being essential as it usually takes the oil pump a minute or more to deliver oil to the bearings after the motor is started.

It is also desired to point out that the head of the piston is inclined towards the non-pressure side, as indicated by the line 22. During the starting of a motor on a cold morning it is essential to employ an exceedingly rich mixture. A large proportion of this mixture consists of raw unvaporized gasoline which settles on the walls of the cylinder and tends to wash away the lubricating film of oil. The raw unvaporized gasoline collects on top of the piston in this instance and as it is inclined, as shown at 22, the raw gasoline tends to drain downwardly past the rings on the non-pressure side of the piston. It is here scraped off or collected by a groove 22 formed in the u per edge of the piston skirt indicat'ti at 12. Tlie cut away side 9 of the skirt is also grooved as indicated at 23. This groove is directed towards the inner face of the skirt, and it can there drain downwardly between the outer skirt and the inner skirt into the crank case. It is thus kept away from the outer face of the non-pressure side of the skirt and to that extent prevents destruction of the lubricating film.

While certain features of the present invention are more or less specifically described, I wish it understood that various changes may be resorted to within the scope of the appended claims, similarly, that thematerials and finishes of the several parts employed may be such as the manufacturer may decide, or Varying conditions or uses may demand.

Having thus described my invention, what claim and desire to secure by LettersPatent 1. A piston comprising a head, a ring and a skirt portion, said skirt having a major and a minor axis in a horizontal cross section thereof, an arch shaped expansion member mounted interior of the skirt and connected with the head of'the piston, and a pair of lugs forming a connection between the arch shaped member and the minor axis of'the 5 skirt. i

' 2. A piston comprising a head, a ring and an outer skirt portion, an inner arch shaped skirt connected with the head, a pair of wrist pin bosses carried thereby, means securing, the outer skirt with relation to the inner arch shaped skirt, said means comprising a pair of lugs extending from the wrist pin bosses to the lower edges of the skirts and connecting the same, and a third lug centrally disposed between the wrist pin bosses and between the skirts and connecting the same.

3. A piston comprising a head, a ring and an arch shaped inner skirt, said skirt supporting a pair of wrist pin bosses, an outer 3o skirt supported by the inner skirt, said outer skirt being cut away around the wrist pin bosses and presenting grooved slanting surfaces functioning as oil scrapers and collectors, and means for directing the collected oil to the exterior surface of the outer skirt.

4. A piston comprising a head, a ring and an arch shaped inner skirt, said sln'rt supporting a pair of wrist pin bosses, an outer skirt supported by the inner skirt, said outer 40 skirt being cut away around the wrist pin bosses and presenting two pairs of slanting surfaces functioning as oil scrapers and collectors, means for directing the oil collected by one pair of grooves to the exterior surface of the outer skirt at one side hereof,'and means for directing the oil collected by the other set of grooves to the interior surface of the outer skirt.

JULIUS DUSEVOIR. 

